This invention relates to integrated circuits, particularly to memory devices, in either embedded form or stand alone (i.e. discrete) form.
Memory cells in devices, for example static random access memory (SRAM) store logical binary values (i.e. either a logical one or a logical zero). When a memory cell is selected by a word line during a read, the voltage on a latch in the memory cell begins to change the voltages on the bit lines attached to the memory cell (i.e. signal is developing on the bit lines). Because the signal on the bit lines is initially small, a certain amount of time must pass to allow the signal on the bit lines to grow larger. When the signal on the bit lines reaches a certain value, this value may be sensed by a sense amp. The sense amp increases the voltage found on the bit lines so that the signal may be transferred to another part of the memory.
Tracking circuits are often used to determine how much time is used to develop signal on bit lines of a memory. Tracking circuits, for example, include delay lines and dummy word lines. Because tracking circuits are used for signal development, the transistors in the tracking circuits can be activated each time a memory array is read. Because the transistors in the tracking circuits can be activated each time a memory array is read, the transistors may degrade faster than the transistors in the memory array. This degradation in the transistors in the tracking circuits can cause changes in the time allowed for signal development on bit lines of the memory array. Changes in the time allowed for signal development can cause a read of the memory array to fail or cause the read access time to increase leading to timing violations in the data output timing paths. Therefore, it is important to reduce the amount of degradation caused in the tracking circuit.